Now you've done pretty good for yourself. From here, it is a major matter of time, lots of emerging, and some config changes.

Emerge Beginning

The first thing to do is:

"emerge sync"

What this does is updates all the files for your tarball assuring they are all up to date. Releases are common, so emerge sync should be done for every install.
Next, I recommend typing:

"emerge nano"

Nano is a simple text editor, which I prefer over things like VI, as it is easier to operate. Once you have merged nano, type in:

"nano /etc/make.conf"

This will open up the make.conf file. In this file, it allows you to modify the CFlags, and compiling options for emerge. CFlags help optimise the source to your cpu standards, making it faster than other stock code.
For help on CFLAGS, check out this website for your cpu. I also recommend modifying the USE flags under make.conf, as they will also help build the code better for your
computer. For information on USE Flags, look here for the entries you can use.
After this, we need to emerge the kernel for the system. I prefer using the 2.6.x kernel as of now, so I use:

"emerge development-sources"

Which in turn downloads the kernel and then installs it to /usr/src/linux-2.6.4 it should be. So from there you do:

"cd /usr/src/"
"ls"

Read the directories, and look for something like "linux-2.6.#" within there. Then cd into the directory, and type:

"make menuconfig"

Follow the configuration tool, and save your editing. From there do the standard kernel compiling things, such as make modules, make modules install, make bzImage, and so on. Then copy System.map and bzImage to /boot for later.

Emerge Some More!

Once you have completed that, you should begin emerging packages. The packages I would emerge would be as followed:

XFREE, IceWM, sysklogd, dcron, grub

Those should get you off the ground and moving. Also, emerge any additional packages that you know nessisary to have to get started. This is all I need, and you shouldn't need much more.

Grub/FSTAB

Now you will need to do some hard drive configuration, with a bootloader and fstab. after emerging grub, type in:

"grub"

Which runs the grub console. First, you need to set a root directory. The root directory will be your Gentoo installation, and it will look for the configuration files here. To do this, you type:

"root (hd0,#)"
"setup (hd0)"

Now this setup will first say the root is located on the Gentoo installation partition. As for setup (hd0) this will tell it to install into the MBR so if you have an alternative configuration, modify it accordingly. Check the offical Gentoo Docs for help also if needbe.
Bare in mind also that in grub, all the disks are set back one, as 0 qualifies as a disk. So, if you want it installed to the mbr, you must have zero on there, and if the Gentoo partition is say hda5, make it hda4 instead.
After this, you type in:

"quit"

Then type:

"nano -w /boot/grub/grub.conf"

This will create a new grub configuration file for it to follow. Though it is an annoyance to do yourself, it is not very difficult. First, you set your timeout, which I set to 30 (30 seconds that means). The default I leave to 0 (zero).
Now if you're like me, you're also dualbooting another Linux/BSD/Windows installation, so you'll probably want to setup these in the config too. For this example, I leave it easy with the Gentoo and the Windows entries. Mine looks something like this:

And this should generally get your grub working. From there, either type:

"reboot"

Otherwise just hit the reboot button on the case. From there, if all went over well, you should see grub popup with your entries in it. Check both to make sure they're working correctly.

Assuming they are, you can boot into Gentoo, and begin working! Make sure that X has a configuration file, and everything is working. Don't forget, since you emerged gdm, you should be able to run it (with a proper XF86Config) and login to IceWM right away.

Thanks for taking a look at my guide. If you need any help, feel free to email me for help.